Indicating system for detecting gaseous and non-gaseous states

ABSTRACT

A detection system capable of distinguishing between a gaseous state and a non-gaseous state such as a liquid state and/or an ice state including a piezoelectric crystal, an exciter circuit connected to the crystal for producing an alternating current output at the mechanical frequency of the crystal, a measuring circuit connected to the output of the exciter circuit for determining increases and decreases in the amplitude of the output signal, and a signal device connected to the measuring circuit and responsive to increase and/or decrease in measurement of the signal output to produce a signal advisory of the change in the ambient physical conditions to which the crystal is subject in the selected location to advise the presence and/or absence of ice or liquid states relative to a gaseous state or to operate another system in response to the change.

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i 541 INDICATING SYSTEM FOR DETECTING GASEOUS AND non- GASEOUS STATESPrimary Examiner-Donald J. Yusko Assistant Examiner-Daniel MyerArtorney-Wiiliam T. Sevald 3,766,981 Dec.19,1 972 57 ABSTRACT Adetection system capable of distinguishing between a gaseous state and anon-gaseous state such as a liquid state and/or an igLSLaLLincluding apiezoelectric crystal, an exciter circuit connected to the crystal forproducing an alternating current output at the mechanical frequency ofthe crystal, a measuring circuit connected to the output of the excitercircuit for determining increases and decreases in the amplitude of theoutput signal, and a signal device connected to the measuring circuitand responsive to increase and/or decrease in measurement of the signaloutput to produce a signal advisory of the change in the ambientphysical conditions to which the crystal is subject in the selectedlocation to advise the presence and/or absence of ice or liquid statesrelative to a gaseous state or to operate another system in response tothe change.

-t glairns Drawing Figures 39 4.2 a: l 24 3k 36 FETjj 4 a o I o 0 c 5PIEZOELECTRIC Z3 CRYSTAL AV.- l

INDICATING SYSTEM FOR DETECTING GASEOUS AND NON-GASEOUS STATES Thisinvention relates to a system to detect and signal the change in ambientphysical conditions from a gas state to a non-gas state such as a liquidand/or ice state; or the reverse; dependant on the state considerednormal.

An object of the invention is to provide a system for detecting theformation of ice where considered undesirable such as on airplane wings,in carburetors, on refrigeration coils, on roads, bridges, etc., and toprovide a warning signal to pilots, drivers, and others.

An object of the invention is to provide a system for detecting andwarning of the absence of ice where considered desirable such as in foodfreezers, etc.

An object of the invention is to provide a system for detecting andwarning of the absence of a liquid where considered desirable, such as adrop below the desired level of oil in the crankcase of an engine,coolant in a radiator, etc.

An object of the invention is to provide a system for detecting andwarning of the presence of a liquid where considered not desirable'suchas rising above a desired level of water in the bilge of boats and intanks, etc.

These and other objects of the invention will become apparent byreference to the following description of a system embodying theinvention, taken in connection with the accompanying drawing, in which:

FIG. 1 is a side elevational view of a crystal and supporting bodyincluding mounting means.

FIG. 2 is a reduced showing of the device seen in FIG. I mounted on atank.

FlG. 3 is a schematic showing of the device mounted on a bridge surfacesubject to icing conditions; and

FIG. 4 is a schematic wiring diagram including the crystal, excitercircuit, measuring circuit, and warning signal device.

Referring now to the drawing wherein like numerals refer to like andcorresponding parts thoughout the several views, the device and systemdisclosed therein to detect a change in ambient physical conditions andto provide a signal on a change occuring comprises a quartz, bariumtitanate, lead zirconate titanate, or other suitable crystal which ispiezoelectric in character to provide a probe or sensor having a naturalmechanical frequency of vibration in air or gas at a certain amplitudeand a damped amplitude of vibration in mediums more viscous than gassuch as ice and liquid. The crystal 10 is mounted on a body 11 whichincludes a threaded nose 12 for mounting the body 11 on a member such asa tank 13, a nut portion 14 for turning with a wrench, a housing 15 forcontaining electrical equipment, and a connector 16 for makingelectrical connections to a power source, to another system controlled,etc.

Referring to FIG. 3, the crystal 10 is integrated in a bridge roadsurface 50. The amplitude of vibration of the crystal 10 is fed to thecircuit in a housing 51. The

output signal from the circuits in the housing 51 is supplied throughwires 52 and 53 to a warning lamp 54.

Referring to FIG. 4, power is supplied to terminals 20 and 21 andlines'22 and 23 respectively. A current limiting resistor 24in line 22and a zener diode 25 in line 26 provide a regulated voltage for theoscillator circuit now described. Resistors 30 and 31 and a capacitor 32form a biasing network for a transistor 33.

An inductor 34 and a capacitor 39 are connected through the transistor33 and form an anti-resonant circuit at the frequency at which thecrystal 10 is antiresonant in the desired crystal mode. This causes thecrystal 10 to vibrate and an alternating voltage of the crystalfrequency is supplied across inductor 34.

In this arrangement, the voltage may be about 10 volts at a frequency of300 KHZ. An inductor 35, is a link which is inductively coupled with theinductor 34 forming an air-core transformer. The voltage which isinduced into the inductor 35 by the inductor 34 is halfwave rectified bya diode 36 and filtered by a capacitor 37 and a resistor 38. Thisresults in direct current voltage across the capacitor 37 and theresistor 38. This voltage acts as a forward bias to hold a transistor 40in an on state.

With transistor 40 on, the bias current through a resistor 41 is shuntedto ground and a transistor 42 is in the off" state and a signal deviceor indicator 43 is off.

Should the vibration of the crystal 10 be damped by the application orimmersion of the crystal 10 in ice or liquid, the on" bias to transistor33 is substantially reduced or eliminated and little or no outputvoltage lies across the inductor 34.

This reduction or loss of voltage across the inductor 34 results in aloss of forward bias on a transistor 40 and the transistor 40 turns off.This in turn allows a forward bias current from a resistor 41 to flow toa transistor 42. This turns the transistor 42 on and passes currentthrough an indicator 43. The output signal to the indicator 43 is alsoavailable at 44 for control of remote devices, functions, or signals.

The position and/or location of the crystal 10 and/or the electricallogic may be established to provide operation of a signal in eithermode; that is, to activate the signal when the crystal is damped byliquid or undamped by liquid or to activate the signal when the crystalis clamped by ice or undamped by the absence of ice.

The invention provides a simple, economical and re liable system anddevice for the detection of ice which has long been sought by theaircraft, air conditioning, refrigeration, transportation, and roadsafety industries, among others.

In aviation, ice is a substantial flight hazard of two types; structuralice and carburetor ice. The latter is particularly insidious because itis concealed from the pilot and where the carburetor may be as much as Flower in temperature than the ambient air with the result that the airin passing through the carburetor is frequently cooled to a temperaturebelow its dew point and the moisture contained in the air is condensedout and freezes on the internal surfaces of the carburetor.

Aircraft equipped with carburetors are normally also equipped with avalve by which the pilot may channel 1 heated air through thecarburetor. The invention provides a ready automatic means ofdetermining exactly when and in what quantity to apply heat to thecarburetor upon the actual formation of ice and to operate the heatvalve.

Another application of the invention is the detection of structural iceon aircraft and in air conditioning and refrigeration systems so thatthe system may initiate automatic operation of de-icing means,defrosting cycles, and perform other tasks.

iosoii r one;

Another application of the invention is road surface ice on bridges suchas shown in FIG. 3. Here there is no residual ground heat factor andupon icing conditions the road surface of the bridge becomes iced priorto the remainder of the road. With the device of the invention on thebridge road surface or other road surfaces, the lamp 54 will provide awarningv While a bridge is used for illustration, the device of theinvention may be used on other road surfaces, sidewalks, ramps, schoolcrossings, etc.

Another application of the device is the sensing of liquid levelsbecause of its unique set of attributes which make it desirable in mayapplications.

The desirable attributes and characteristics of the device of theinvention include all solid-state with no moving parts, highreliability; extreme sensitivity and accuracy; capabilities of detectionof non-conductive fluids such as oils and gasolines; ability to operateover extremely wide temperature ranges; and no fire hazard.

While only a few exemplary embodiments of the device has been shown anddescribed with exemplary circuits, it will be understood that the scopeof the invention is defined by the appended claims.

I claim:

1. A detecting system for distinguishing between a gaseous environmentalphysical condition and environmental physical conditions other thangaseous such as liquid, ice, etc., by a stronger output signal in thepresence' of a gas, and a weaker output signal in the presence ofconditions other than gas, comprising,

a piezoelectric crystal exposabl e to environmental physical conditionsin a selected location;

said crystal having a mechanical frequency of vibra tion affected by thedensity of ambient physical conditions resulting in a normal undampedrelatively stronger amplitude of vibration .in the presence of gaseousconditions and a damped weaker amplitude of vibration in the presence ofconditions other than gaseous;

a body supporting said crystal;

means on said body for mounting said body on a member to expose saidcrystal to ambient physical conditions in a selected location;

an exciter circuit including said crystal producing an alternatingcurrent output at the normal frequency of said crystal;

a signal circuit connected to said exciter circuit output for measuringsaid exciter circuit output; and a signal device connected to saidsignal circuit responsive to measurement of said output to advise changein ambient physical conditions occurring bi-directionally between agaseous state and a non-gaseous state at the selected location toprovide a signal indicating that a change has occurred in ambientphysical conditions and indicative of the present state(.); said excitercircuit including a current limiting resistor and a zener diode toprovide a regulated voltage for anoscillator circuit leading to said'piezoelectriccrystal;

said exciter circuit having an oscillator circuit leading from saidpiezoelectric crystal including an FET transistor, resistors, and acapacitor forming a biasing network for said transistor; and

an inductance and a second capacitor connected through said transistor;

said circuit causing said crystal to vibrate and produce an alternatingvoltage of the crystal frequency across said inductance; should thevibration of said crystal be damped, the ON" bias 5 to said transistoris reduced and output voltage is reduced. 2. In a system as set forth inclaim I, an inductor coupled with said inductance receiving inducedvoltage, a diode rectifying said voltage to half wave D.C., a capacitorand a resistor filtering the direct current from said diode, a secondtransistor receiving said direct current holding it in the ON" state;

a third transistor and a resistor receiving voltage from said secondtransistor normally biasing said third transistor OFF, and an indicatorconnected to said third transistor;

should the predetermined vibration of said piezoelectric crystal bedamped, ON" bias to said second transistor is reduced and it turns to anOFF state whereupon said third transistor loses its 0FF" bias and turnsto an "ON state powering said indicator.

3. A detecting system including an oscillator circuit for responding tothe presence and absence of a gaseous condition relative to anon-gaseous condition, comprising a piezoelectric crystal exposable toenvironmental gaseous and non-gaseous conditions;

said crystal producing vibrations when powered;

means powering said crystal to cause said crystal to vibrate including acurrent limiting resistor and a zener diode leading to an oscillator toprovide a regulated voltage output to said oscillator circuit and saidcrystal;

an oscillator circuit including a field effect transistor having aninput side, a first output side, and a second output side; said inputside being connected to said crystal output; at least one resistor and acapacitor connected to said first output side of said transistor forminga bias for said transistor; an inductance and a capacitor connected tosaid second output side of said transistor for receiving voltage fromsaid crystal through said transistor;

said crystal when in a gaseous condition being undamped to producevoltage to modulate said transistor bias to cause said transistor tooscillate and when in a non-gaseous condition being damped to produceunmodulated transistor bias to cause said transistor not to oscillate;

the presence of voltage at said inductance thereby providing a signalindicative of a gaseous state at said crystal and the absence of voltageat said inductance thereby providing a signal indicative of anon-gaseous state at said crystal.

4. In a system as set forth in claim 3, an inductor coupled with saidinductance receiving induced voltage, a diode rectifying said voltage tohalf wave D.C., a capacitor and a resistor filtering the direct currentfrom said diode, a second transistor receiving said direct currentholding it in the ON" state;

a third transistor and a resistor receiving voltage from said secondtransistor normally biasing said third transistor OFF", and an indicatorconnected to said third transistor;

should the predetermined vibration of said piezoelectric crystal bedamped, ON" bias to said l060ll 0787 second transistor is reduced and itturns to an OFF state whereupon said third transisior loses its "OFFbias and turns to an ON" state powering said indicator.

* is w 5

1. A detecting system for distinguishing between a gaseous environmentalphysical condition and environmental physical conditions other thangaseous such as liquid, ice, etc., by a stronger output signal in thepresence of a gas, and a weaker output signal in the presence ofconditions other than gas, comprising, a piezoelectric crystal exposableto environmental physical conditions in a selected location; saidcrystal having a mechanical frequency of vibration affected by thedensity of ambient physical conditions resulting in a normal undampedrelatively stronger amplitude of vibration in the presence of gaseousconditions and a damped weaker amplitude of vibration in the presence ofconditions other than gaseous; a body supporting said crystal; means onsaid body for mounting said body on a member to expose said crystal toambient physical conditions in a selected location; an exciter circuitincluding said crystal producing an alternating current output at thenormal frequency of said crystal; a signal circuit connected to saidexciter circuit output for measuring said exciter circuit output; and asignal device connected to said signal circuit responsive to measurementof said output to advise change in ambient physical conditions occurringbi-directionally between a gaseous state and a non-gaseous state at theselected location to provide a signal indicating that a change hasoccurred in ambient physical conditions and indicative of the presentstate(.); said exciter circuit including a current limiting resistor anda zener diode to provide a regulated voltage for an oscillator circuitleading to said piezoelectric crystal; said exciter circuit having anoscillator circuit leading from said piezoelectric crystal including anFET transistor, resistors, and a capacitor forming a biasing network forsaid transistor; and an inductance and a second capacitor connectedthrough said transistor; said circuit causing said crystal to vibrateand produce an alternating voltage of the crystal frequency across saidinductance; should the vibration of said crystal be damped, the''''ON'''' bias to said transistor is reduced and output voltage isreduced.
 2. In a system as set forth in claim 1, an inductor coupledwith said inductance receiving induced voltage, a diode rectifying saidvoltage to half wave D.C., a capacitor and a resistor filtering thedirect current from said diode, a second transistor receiving saiddirect current holding it in the ''''ON'''' state; a third transistorand a resistor receiving voltage from said second transistor normallybiasing said third transistor ''''OFF'''', and an indicator connected tosaid third transistor; should the predetermined vibration of saidpiezoelectric crystal be damped, ''''ON'''' bias to said secondtransistor is reduced and it turns to an ''''OFF'''' state whereuponsaid third transistor loses its ''''OFF'''' bias and turns to an''''ON'''' state powering said indicator.
 3. A detecting systemincluding an oscillator circuit for responding to the presence andabsence of a gaseous condition relative to a non-gaseous condition,comprising a piezoelectric crystal exposable to environmental gaseousand non-gaseous conditions; said crystal producing vibrations whenpowered; means powering said crystal to cause said crystal to vibrateincluding a current limiting resistor and a zener diode leading to anoscillator to provide a regulated voltage output to said oscillatorcircuit and said crystal; an oscillator circuit including a field effecttransistor having an input side, a first output side, and a secondoutput side; said input side being connected to said crystal output; atleast one resistor and a capacitor connected to said first output sideof said transistor forming a bias for said transistor; an inductance anda capacitor connected to said second output side of said transistor forreceiving voltage from said crystal through said transistor; saidcrystal when in a gaseous condition being undamped to produce voltage tomodulate said transistor bias to cause said transistor to oscillate andwhen in a non-gaseous condition being damped to produce unmodulatedtransistor bias to cause said transistor not to oscillate; the presenceof voltage at said inductance thereby providing a signal indicative of agaseous state at said crystal and the absence of voltage at saidinductance thereby providing a signal indicative of a non-gaseous stateat said crystal.
 4. In a system as set forth in claim 3, an inductorcoupled with said inductance receiving induced voltage, a dioderectifying said voltage to half wave D.C., a capacitor and a resistorfiltering the direct current from said diode, a second transistorreceiving said direct current holding it in the ''''ON'''' state; athird transistor and a resistor receiving voltage from said secondtransistor normally biasing said third transistor ''''OFF'''', and anindicator connected to said third transistor; should the predeterminedvibration of said piezoelectric crystal be damped, ''''ON'''' bias tosaid second transistor is reduced and it turns to an ''''OFF'''' statewhereupon said third transistor loses its ''''OFF'''' bias and turns toan ''''ON'''' state powering said indicator.